An approximate analysis is presented for the elastic-plastic bending of a moderately thick plate at large deflection. The analysis is carried out on a simplified model representing the solid plate, and behavior is examined through several stages starting from the linear elastic range of pure bending and terminating at collapse as a plastic membrane. The theoretical work is compared against experimental data obtained by testing plates under uniform static loading in a specially designed pressure cell. The investigation is restricted initially to the problem of a plate with edges pinned yet free to move in the plane of the plate. In a sense, this investigation is complementary to previous upper bound, post-collapse analyses of plates carried out in the spirit of plastic-rigid, large deflection theory.